The known state of the art includes arrangements for checking documents, by passing light simultaneously through an original or master and a document, where the original is sensitive to light and is intended to emit respectively an intensity maximum and an intensity minimum for the light energy derived from a light source and passing through the documents and the original. An example of one such arrangement is disclosed in Swedish Patent Specification 353 807.
Also known to the art are document checking arrangements which incorporate thickness measuring devices which are operative in measuring continuously thicknesses within an area whose form corresponds to the form of given parts of the document having a thickness different to remaining document parts. An example of one such arrangement is disclosed in Swedish Patent Specification 355 428.
These and similar document checking arrangements have, in some cases, been found much too expensive in manufacture and in operation to be used successfully in large numbers, for instance in conventional automatic cash dispensers.